Metal boat for sinter furnace

ABSTRACT

A METAL BOAT FOR CARRYING WORKPIECES THROUGH A HIGH TEMPERATURE SINTER FURNACE IS COMPOSED OF A THICK AND VERY RIGID SHOCK-RESISTANT BOTTOM PLATE UPON WHICH A THIN SHEET METAL FRAME IS REMOVABLY MOUNTED, THE PLATE AND FRAME BEING COMPOSED OF MOLYBDENUM OR ALLOYS THEREOF.

Jan. 12, 1971 arwespz ETAL 3,553,800

METAL BOAT FOR SINTER FURNACE Filed Dec. 23, 1968 0 o o o o o o o o o o o o o o o v o o o o o o o 0 0 0 o 0 Q o o o o INVENTORS Friedrich Player Harm Roepenack Klaus Wagner United States Patent 3,553,800 METAL BOAT FOR SINTER FURNACE Friedrich Pliiger, Kleinostheim, Horst Roepenack, Bruchkiibel, and Klaus Wegner, Hanan, Germany, assignors to NUKEM, Nuklear-Chemie und Metallurgie Gesellschaft mit beschrankter Haftung, Hanan am Main, Germany Filed Dec. 23, 1968, Ser. No. 786,102

Claims priority, application Germany, Dec. 30, 1967,

Int. Cl. F27d /00 US. Cl. 25-153 4 Claims ABSTRACT OF THE DISCLOSURE A metal boat for carrying workpieces through a high temperature sinter furnace is composed of a thick and very rigid shock-resistant bottom plate upon which a thin sheet metal frame is removably mounted, the plate and frame being composed of molybdenum or alloys thereof.

This invention relates to metal boats for transporting workpieces through a high temperature furnace.

A high temperature furnace is an essential component in the technology of sintered ceramics. Pre-shaped ceramic powders such as oxides, nitrides and heavy metal carbides, are sintered in the high temperature furnace into bodies having high, density and mechanical stability. Many of the ceramic powders and especially the transition metals in Groups III to VI of the Periodic System require temperatures which preclude metal boats made out of high melting steels as, for example, Cr-Ni for transporting the pre-shaped ceramic bodies. The furnaces which operate at temperatures above 1300 C. are lined with a ceramic material and the boats for transporting the ceramic workpieces are composed preferably of molybdenum or special molybdenum alloys. The molybdenum boats are formed either as a deeply drawn container having a low height or as welded or riveted containers made of molybdenum sheet metal. Molybdenum alloys have the advantage in that their heat stability is greater than that of pure molybdenum. Welded and riveted metal boats have performed poorly in gravity discharge furnaces customarily used in practice because the boats deform rather quickly under the thrust forces they receive. Such deformations lead rather quickly to furnace damage and interruption because the boats jam in the furnace channel which is another reason Why they have a rather limited use life in furnaces operating at high temperatures of, for example, 1600 to 1800 C.

In order to prevent the deformation of the molybdenum boats as much as possible, it has been suggested to carry the molybdenum boats through the gravity discharge furnace on ceramic plates having an approximate thick ness of from 2 to 3 cm. and preferably composed of A1 0 This suggestion has not been entirely satisfactory in practice because the ceramic material is sensitive to thermo-shock and can only withstand a few temperature changes when used in the customary high temperature gradients in the furnace.

The object of this invention is to produce a metal boat for transporting workpieces through a sinter furnace which can hold up under the operating conditions.

In general this and other objects of the invention are obtained by forming a boat having a very rigid bottom plate for absorbing the thrust force with a thin metal frame mounted on top of the plate, which construction withstands deformation in the furnace while not being limited to the limited height of a deeply drawn thickwalled boat and the quick deformation of welded or riveted sheet metal boats made of molybdenum.

, In this invention, the boat has a sturdy bottom plate approximately 15 to 20 mm. thick which is made of molybdenum or any suitable molybdenum alloy. This bottom plate functions to absorb thrust forces produced in the furnace. Therefore, the bottom plate can be constructed as a heavy plate or can be reduced in weight by being machined without losing rigidity.

The means by which the objects of the invention are obtained are described more fully in the accompanying drawings in which:

FIG. 1 is a plan view of the boat; and

FIG. 2 is a side view of FIG. 1 shown partly in section.

As shown in the drawings, the bottom heavy plate 1 can be milled to form channels or recesses 4 or the like for reducing the weight of the plate but, however, retaining the overall rigidity of the plate. A thin sheet metal frame 2 composed of molybdenum is removably mounted on plate 1 for surrounding the space occupied by the workpieces composed of sinter material. Since frame 2 is not subject to any thrust forces, it can be made of thin molybdenum metal sheets to any desired height. If it is necessary that a reaction gas enter the sinter material as, for example, in the reduction to stoichiometric U0 before and/or during the sintering process, then the frame is provided with perforations 3. The perforated frame with the larger height as well as the greater resistance of the bottom plate to deformation forces permits for each molybdenum boat a much higher load capacity and thus a substantial increase in the furnace capacity. Also, the boat having the removable frame 2 has the advantage that it can be produced more easily and better in an automatic assembly line. Furthermore, the boat is much more durable than a deeply drawn boat.

The alloys from which the boats of this invention are made are 1.5% titanium, 0.07% zirconium, remainder molybdenum or 30% tungsten and molybdenum.

High temperature resistant steel can be used instead of molybdenum when lower sintering temperatures are used in the furnace.

Having now described the means by which the objects of this invention are obtained.

We claim:

1. A metal boat for carrying workpieces through a sintering furnace comprising a thick and very rigid thrust shock-resistant bottom plate, a thin sheet metal frame removably mounted on said bottom plate, and said plate and frame being composed of molybdenum or alloys thereof.

2. A boat as in claim 1 in which said frame is perforated.

3. A boat as in claim 1 in which said plate and frame are an alloy composed of 0.5% titanium, 0.07% zirconium, and the remainder molybdenum.

4. A boat as in claim 1 in which said plate and frame are an alloy composed of 30% tungsten and 70% molybdenum.

References Cited UNITED STATES PATENTS 12/1918 Owens 25-153 5/1963 Smoot 25-153 

